By: Marta San Luciano
SUNY Downstate Medical Center
In April’s issue of Archives of Neurology, researchers from the University of Maryland presented the results of a study on racial and socioeconomic differences in patients with parkinsonism from their Movement Disorders Center in Baltimore. They found that African-American patients had greater disability and disease severity as compared to Caucasian patients, and that they were also less likely to be prescribed dopaminergic medications.
It is known that racial and ethnic minorities have worse access to healthcare and poorer health outcomes, and that these differences are not entirely explained by differences in social and economic status. Understanding the factors underlying racial disparities provides useful information for designing quality improvement interventions to minimize social barriers and provide excellent neurologic care to all patients. We are just beginning to identify such disparities in Parkinson’s disease (PD).
Racial and ethnic disparities in PD are a complex issue. Studies have shown that US Black PD patients are less likely to be diagnosed as having PD, and less likely to be prescribed medications and to undergo deep brain stimulation (DBS) surgery. Non-White minorities are also known to be under-represented in clinical trials for PD. Inequities in the health delivery system and socioeconomic disparities may be partly accountable. However, one study from the VA, in an integrated healthcare system where barriers limiting access to care are lower, showed that non-White veterans were 15% less likely to receive high quality PD care. What may explain these disparities?
First, PD may be under-diagnosed in non-White populations. Whether PD is less common in Blacks and other ethnic minorities has been a matter of debate. Several epidemiological studies have suggested that Blacks may be less likely to develop PD than Whites, but other studies have reported similar disease rates. Epidemiologic door-to-door studies show that Blacks may be more likely to be undiagnosed. Cultural and educational differences may prevent patients from seeking appropriate care, particularly at early stages, when symptoms are not yet disabling. One study showed that Blacks more than Whites may see parkinsonian symptoms as an inevitable part of aging and dementia more as a natural result of living a difficult life. Healthcare providers may fail to identify the cardinal symptoms of PD in certain populations because of under-training or bias. Primary care physicians treating Black patients have been shown to be less clinically trained, and it is a fact that racial and ethnic minorities receive care disproportionately in lower-performing institutions, and may have geographical barriers to specialized treatments, such as DBS.
In addition, PD in certain non-White populations may be clinically different. Neurodegenerative diseases, PD among them, are clinico-pathological entities almost exclusively defined in White populations. It is difficult to determine then whether the disease is similar across different ethnic groups, because of a paucity of studies in non-Whites. Race and ethnicity modulate diseases via genetic background, therefore, PD symptoms and signs may be expected to differ across different ethnicities. In PD, two studies from Nigeria observed more frequent atypical features in African Black PD patients, but data from the US is lacking. Blacks suffer higher morbidity from hypertension and diabetes than Whites, and Black under-representation in clinical trials may be due to Blacks having additional medical conditions, such as high blood pressure. It is also possible that differences in the cause of PD in different populations may be due to genetic factors, which are more common in certain groups. For example, major genetic mutations associated with PD that are frequently found in European populations are not readily found in Sub-Saharan Africans.
Lastly, patient-related socioeconomic and cultural factors, as well as physician preferences, may influence starting treatment and the choice of medications. In turn, possible differences in disease etiology and clinical presentation may influence response to PD medications. For example, in a trial of the dopamine agonist pramipexole, the frequency of some side effects varied by ethnicity.
In conclusion, a complex relation of healthcare access and quality, biology and socio-cultural factors underlie racial and ethnic differences in PD. There is a need to tease out the causal mechanisms underlying Parkinson’s disease outcomes in patients of different backgrounds, so that interventions can be developed to eliminate inappropriate disparities and improve quality of life for all our patients.
Dr. Marta San Luciano received her M.D. degree from the University of Navarre in Spain, and her MS in clinical research methods from Albert Einstein College of Medicine. She completed her residency in Neurology at Boston University Medical Center in 2007 following her internship in Internal Medicine at Metropolitan Hospital in New York. During 2007-2010 she served as a clinical and research fellow in Movement Disorders at Beth Israel Medical Center. She was awarded a Clinical Research Training Fellowship Award by The American Academy of Neurology in 2008 and Currently, she is an Assistant Professor of Neurology at the State University of New York (SUNY) Downstate Medical Center, an NPF Center of Excellence.